1. Field of the Invention
This invention relates to concrete load bearing columns and, more particularly, to forms for forming concrete load bearing columns to hold posts in place and support the weight of the post.
2. Description of the Prior Art
The concrete foundation for residential decks and the like, anchors the entire structure against settling, slippage and wind lift. It also distributes loads into the ground and protects posts or beams from direct contact with the earth. The foundation may consist of two parts, a footing that distributes the load underground and a pier that raises the bottom of the post above grade or in many installations just one part the pier, performs both functions.
The size and depth of footings are governed by local building codes. Typical footings extend at least 6 inches below the frost line.
The piers can be cylindrical, rectangular or pyramidal with a flat top. The pier should hold the bottom of the post at least 2 inches above grade to protect it from decay. There are three basic methods of constructing the foundation: (1) casting a footing then placing a precast pier on it (2) casting both the footing and the pier using wooden forms and (3) using fiber tubes to cast a cylindrical column.
Fibre tubes generally come in 6", 8", 10" and 12" diameters and can be cut to any length. In utilizing fiber tubes some manufacturers recommend that a hole be dug twice as wide as the tube diameter. Local building codes specify the depth of the hole. Loose gravel (2 to 3 inches) may be provided in the bottom of the hole to provide drainage under the concrete footings. A four to six inch footing may then be optional poured into the bottom of the hole. The tube is cut at least 2 inches longer than the depth of the hole so that the column will be above ground level. The tube is placed in the hole and a level used to insure the top of the tube is level. Soil is then packed around the tube to hold it in place. Alternatively the tube is braced with light lumber. The tube is then filled with concrete and the concrete tapped into place using a long stick or bar to fill any air gaps. The concrete is levelled to the top of the tube. A beam or post anchor can then be inserted into the wet concrete at the center of the tube. After the concrete cures, any exposed portion of the tube is cut away with a utility knife.
For a 6".times.48" tube two or more bags of concrete mix are usually required to fill the tube. An 8".times.48" tube requires about three bags of concrete mix.
To store the tubes they are either stacked horizontally or vertically which requires considerable floor space and cargo space when the forms are transported to a site.